feat(dashboard): expand IDE workspace editing

[golemcore1]

Summary

• Expand the dashboard IDE backend file API with workspace downloads, upload support, lazy tree parameters, ignored/generated directory filtering, and file metadata for binary/image/editable states.
• Add dashboard IDE image/binary previews, upload/download controls, ignored-file toggle, breadcrumbs, command palette, editor search bar, and editor display settings.
• Extend IDE tab/content state so non-editable images and binary files open as previews instead of attempting UTF-8 editing.
• Add regression coverage for backend file metadata/upload/download/tree behavior and frontend image/binary preview rendering.

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
93.5% Coverage on New Code
1.4% Duplication on New Code

See analysis details on SonarQube Cloud